a. Field of the Invention
The present invention relates to ultrasound catheters and sheaths and methods of using ultrasound catheters and sheaths. More particularly, the present invention relates to a control handle for steerable sheaths, methods of manufacturing and using such a handle, an ultrasound catheter for use with the steerable sheath, and methods of using the combination of the ultrasound catheter and sheath.
b. Background Art
Catheters (i.e. catheters or sheaths) that have flexible tubular bodies with deflectable distal ends and control handles for controlling distal end deflection are used for many invasive medical procedures. For example, catheters having conductive electrodes along the distal ends of their bodies are commonly used for intra-cardiac electrophysiology studies. The distal end of a catheter body is typically placed into a patient's heart to monitor and/or record the intra-cardiac electrical signals during electrophysiology studies or during intra-cardiac mapping. The orientation or configuration of the distal end is controlled via an actuator located on the catheter's control handle, which remains outside the patient's body. The electrodes conduct cardiac electrical signals to appropriate monitoring and recording devices that are operatively connected at the control handle.
Typically, a catheter body is cylindrical and electrically non-conductive. The catheter body includes a flexible tube constructed from polyurethane, nylon or other electrically non-conductive flexible material. The catheter body further includes braided steel wires or other non-metallic fibers in its wall as reinforcing elements. Each electrode has a relatively fine electrically conductive wire attached thereto and extending through the catheter body. The conductive wire extends from the distal end to a proximal end where electrical connectors such as plugs or jacks are provided to be plugged into a corresponding socket provided in a recording or monitoring device.
The distal portion of the catheter body is selectively deformed into a variety of curved configurations using the actuator on the control handle. The actuator is commonly internally linked to the distal portion of the catheter body by at least one deflection wire. Some catheter bodies employ a single deflection wire, which is pulled (i.e. placed in tension) by the actuator in order to cause the distal portion of the catheter body to deform. Other catheter bodies have at least two deflection wires, where the displacement of one wire (i.e., placing one wire in tension) results in the other wire going slack (i.e., the wire does not carry a compressive load). In such catheters, where the deflection wires are not adapted to carry compressive loads (i.e., the deflection wires are only meant to be placed in tension), the deflection wires are commonly called pull or tension wires.
Prior art control handles are often inadequate with respect to their ability to provide the finely controlled deflection adjustment for the distal end of the catheter body necessary to target a particular anatomy with an ultrasound catheter. The prior art control handles often provide inadequate deflection wire travel for a desired viewing angle or orientation. The control handles often have a mechanical advantage that is less than desirable and, as a result, require significant effort to operate on the part of a user. Moreover, it is desirable that the physician be able to set the ultrasound catheter at a particular viewing angle and have it stay set. However, with prior art catheters the control handles typically require the physician to take a conscious step to maintain the catheter at the desired deflection.
One type of instrument catheter is an ultrasound visualization catheter, such as an intracardiac echocardiography (ICE) catheter, which includes ultrasound elements or arrays on the distal end of the catheter. The ultrasound elements are useful for visualizing particular portions of the cardiac anatomy under study. The typical ultrasound catheter aims a two dimensional beam or fan at a portion of the anatomy and provides the clinician with a visual of the anatomy under study. Because the fan may be both narrow and small, and of limited range, precise adjustments are often necessary in order to successfully view particular anatomy. Thus, the ability to adjust the orientation or direction of an ultrasound fan precisely, with minimal or no deformation of the catheter, is important in using an ultrasound catheter. Providing a handle with fine motor control and a desirable mechanical advantage also has specific utility for an ultrasound catheter. In particular, there is a need in the art for a catheter system that offers improved operation and deflection adjustment of the distal end of the ultrasound catheter body. There is also a need in the art for a method of manufacturing and using such a catheter system.